Molecular networking-based mass spectral identification of Brucea javanica (L.) Merr. metabolites and their selective binding affinities for dengue virus enzymes.

Brucea javanica, a valued traditional medicinal plant in Malaysia, known for its fever-treating properties yet remains underexplored for its potential antiviral properties against dengue. This study aims to simultaneously identify chemical classes and metabolites within B. javanica using molecular networking (MN), by Global Natural Product Social (GNPS), and SIRIUS in silico annotation. Liquid chromatography-mass spectrometry (LC-MS2)-based MN explores chemical diversity across four plant parts (leaves, roots, fruits, and stem bark), revealing diverse metabolites such as tryptophan-derived alkaloids, terpenoids, and octadecadenoids. Simultaneous LC-MS2 and MN analyses reveal a discriminative capacity for individual plant components, with roots accumulating tryptophan alkaloids, fruits concentrating quassinoids, leaves containing fusidanes, and stem bark primarily characterised by simple indoles. Subsequently, extracts were evaluated for dengue antiviral activity using adenosine triphosphate (ATP) and plaque assays, indicates potent efficacy in the dichloromethane (DCM) extract from roots (EC50 = 0.3 µg/mL, SI = 10). Molecular docking analysis of two major compounds; canthin-6-one (264) and 1-hydroxy-11-methoxycanthin-6-one (275) showed potential binding interactions with active sites of NS5 RNA-dependent RNA polymerase (RdRp) of dengue virus (DENV) protein. Subsequent in vitro evaluation revealed compounds 264 and 275 had a promising dengue antiviral activity with SI value of 63 and 1.85. These identified metabolites emerge as potential candidates for further evaluation in dengue antiviral activities.

Genetic diversity of Plasmodium knowlesi among human and long-tailed macaque populations in Peninsular Malaysia: The utility of microsatellite markers.

It has been discovered that Plasmodium knowlesi (P. knowlesi) is transmitted from macaque to man. Thus, the aim of the present study was to determine P. knowlesi genetic diversity in both human (n = 147) and long-tailed macaque (n = 26) samples from high- and low-endemicity localities. Genotyping was performed using seven neutral microsatellite loci markers. The size of the alleles, multiplicity of infection (MOI), mean number of alleles (Na), expected heterozygosity (HE), linkage disequilibrium (LD), and genetic differentiation (FST) were determined. In highly endemic P. knowlesi localities, the MOI for human and long-tailed macaque isolates was 1.04 and 1.15, respectively, while the Na was 11.14 and 7.86, respectively. Based on the allele frequency distribution for all loci, and with FST < 0.1, no genetic differentiation was seen between human and long-tailed macaque. In localities characterised by lower P. knowlesi endemicity, the MOI for human and long-tailed macaque isolates was 1.05 and 1.11, respectively, while the Na was 6.14 and 2.71, respectively. Further molecular analysis of the allele frequencies indicated that there was a significant genetic differentiation in human P. knowlesi isolates as compared to long-tailed macaque isolates, with a very low fixation index (FST = 0.016, p < .05) based on multiple loci analysis. Our results further indicate that, in Peninsular Malaysia, humans are mostly affected by P. knowlesi of a single genotype, while long-tailed macaque tend to acquire polyclonal infections, which supports the assumption that there is a higher rate of transmission among long-tailed macaque. Understanding the genetic diversity of P. knowlesi isolates can provide invaluable information for characterising patterns of the population structure and the migration rate of P. knowlesi in peninsular Malaysia.

Effect of choline kinase inhibitor hexadecyltrimethylammonium bromide on Plasmodium falciparum gene expression.

Investigations on the fundamental of malaria parasite biology, such as invasion, growth cycle, metabolism and cell signalling have uncovered a number of potential antimalarial drug targets, including choline kinase, a key enzyme involved in the synthesis of phosphatidylcholine, an important component in parasite membrane compartment. The effect on gene expression of Plasmodium falciparum K1 strain following 72 hours exposure to 2 microM (IC50 concentration) of the choline kinase inhibitor, hexadecyltrimethylammonium bromide (HDTAB) was evaluated by DNA microarray analysis. Genes important in P. falciparum intraerythrocytic life cycle, such as invasion, cytoadherance and growth were among those affected by at least 2-fold changes in their expression levels compared with non HDTAB-treated control.